As we all know, when an engine is driven, engine oil is supplied to the friction parts of the engine to lubricate and cool them. As the engine keeps on working, the engine oil is contaminated by oxides and various impurities produced when metal particles, carbon particles, and engine oil are oxidated. If the engine continues to run when the engine oil is contaminated, rotating friction parts such as crankshaft and oil cylinder are gradually worn out and become damaged. If the conditions further worsen, these parts may be sintered causing a risk of safety accidents.
As described above, it is very important to continuously keep engine oil clean because it directly affects the service life and performance of the engine. Therefore, an oil filter assembly needs to be set on the engine oil circulation path to continuously keep engine oil clean.
The following describes in detail the existing oil filter assembly with reference to the drawings.
FIG. 1 is an exploded oblique view of the existing oil filter assembly and FIG. 2 shows the structure of the drain bolt installed on the cap of the existing oil filter assembly.
The existing oil filter assembly comprises the following structures: a casing (10), a replaceable oil filter (20) set in the casing (10), and a detachable cap (30) combined at the opening (15) of the casing (10). A first installation part (11) and a second installation part (12) are formed on the other side of the casing (10). The first installation part (11) is installed on the engine side (not shown in the figure) with a plurality of connection pieces, while the second installation part (12) is installed on the engine oil cooler side (5) with a plurality of connection pieces. In addition, a first oil return hole (11a) connected to the engine (not shown in the figure) and a drain hole (11b) are formed on the first installation part (11), while a second oil return hole (12a) connected to the engine oil cooler (5) and an oil inlet hole (12b) are formed on the second installation part (12). Therefore, contaminated engine oil in the internal circulation of the engine (not shown in the figure) flows through the first oil return hole (11a) and the second oil return hole (12a) into the engine oil cooler (5), and contaminated engine oil is cooled in the engine oil cooler (5). After engine oil cooled in the engine oil cooler (5) flows through the oil inlet hole (12b) into the casing (10) and is filtered by the filter (20) in the casing (10), it is supplied to the engine side (not shown in the figure) through the drain hole (11b).
The filter (20) comprises filter paper (21) corrugated along the circumference and a support supporting the filter paper (21). In addition, a top support plate (22a) and a bottom support plate (22b) are respectively equipped at the top and bottom of the support to support the top and bottom of the filter paper (21), and a flow path (23) which engine oil passes by is formed along the centre of the support.
The cap (30) can detachably be combined with the opening (15) of the casing (10), an external screw part (30a) is formed on the external circumferential surface of the top of the cap (30), and the external screw part (30a) is combined with the internal screw part formed on the internal circumferential surface of the opening (15). In addition, a sealing element (16) is set between the cap (30) and the casing (10), and the cap (30) and the casing (10) are combined in a sealing manner. A bypass valve (40) is formed at the bottom of the flow path (23) of the support, and the bypass valve (40) is combined with the inner side at the centre of the cap (30).
In addition, the nut boss (35) at the centre of the bottom of the cap (30) protrudes downwards, and the metallic drain bolt (50) can detachably be combined with the drain hole (33) in the boss (35). A metallic nut fitting (34) is integrated on the internal circumferential surface of the drain hole (33) by means of insertion and injection and an internal screw part (34a) is formed on the internal circumferential surface of the nut fitting (34). Next, since the external screw part (50a) of the metallic drain bolt (50) is detachably combined with the internal screw part (34a) of the nut fitting (34) in screwed connection mode, the drain bolt (50) can firmly be fixed to the drain hole (33) side of the cap (30). Further, a sealing element (55) is set between the external circumferential surface of the drain bolt (50) and the internal circumferential surface of the nut fitting (34) to ensure the tightness between the drain bolt (50) and the nut fitting (34).
A connecting groove (52), where a wrench can be inserted, is formed at the centre of the head end (51) of the drain bolt (50) and an internal screw part (50a) is formed on the external circumferential surface of the drain bolt (50). As described above, the external screw part (50a) can detachably be combined with the internal screw part (34a) of the drain hole (33). Therefore, when the operator turns the drain bolt (50) to remove it from the cap (30), the drain hole (33) in the cap (30) is opened and engine oil inside said oil filter assembly is discharged out through said drain hole (33).
However, as described above, if the drain bolt (50) is combined with the drain hole (33) in screwed connection mode, when said drain bolt (50) is removed, engine oil flows out of the cap (30), and the drain bolt (50), the working tool, and the hands of the operator get contaminated with engine oil. In addition, it takes a long time to remove the drain bolt (50), and engine oil leaks when the drain bolt (50) is slightly loosened under the action of an external force. These are all disadvantages of the existing oil filter assembly.